INFORMATION TRANSMITTER/RECEIVER

摘要

An information transmitter/receiver for transmitting/receiving specific information having improved efficiencies of the single communication, vendor multicasting, group multicasting, and ciphering/deciphering therefor. An information transmitter sends a key message in which a specific information ciphering key is ciphered by a normal key and then sends a cipher message in which specific information is ciphered by the specific information ciphering key to a destination being an information receiver. The information receiver deciphers the specific information ciphering key contained in the key message by means of a normal key and then deciphers the cipher message following the key message by means of the specific information ciphering key. When there are information receivers which are destinations, the information transmitter sends setting information, such as multicasting setting information for single communication and multicasting, ciphering setting information, vendor setting information, and group setting information to the information receiver.